Fire protection system



June '2, 1 964 E. P. HANSON ETAL FIRE PROTECTION SYSTEM Filed Sept. 28, 1962 I!!! my!!! INVENTORS HANSON PHILIP H. MERDINYAN GORDON H. MILLIGAN ERIC P.

ATTORNEY United States Patent This invention relates to improvements in fire protection systems. More particularly, it has to do with fire protection systems which are designed for use with materials which burn so rapidly and so fiercely that combustion of these materials amounts almost to an explosion.

i The system is designed to operate with such speed that a fire is extinguished, or at least controlled, before 1t reaches such explosive force that surrounding equipment or buildings are either damaged or destroyed, or nearby personnel injured or killed.

This application is a continuation-in-part of our copending application SerialNo. 39,527 for FireProtection System, filed June 29, 1960, now Patent No. 3,064,739, issued Nov. 20, 1962. In that application we disclosed a fire protection system for materials as described above which operates within a very short period of time after the start of afire. The invention of this application is an improvement on our former system and is directed toward still further reducing the time interval between the start of a fire and the application of a fire controlling and extinguishing agent thereto, and also toward increasing the force at which such agent is applied to the burning material, especially during the initial stages of the fire.

Principally, the types of materials for which this systern is designed are rocket fuels, particularly solid rocket propellants. Such fuels, as pointed out in our prior ap- 'plication, substantially explode when ignited, thereby creating a hazard potentially capable of causing vast destruction of property and serious loss of life. Little thought need be given to fully appreciate the necessity for adequate protection against the outbreaks of fire during the manufacture and processing of these materials.

In view of this characteristic of these materials, the systern of our prior application was designed with the basic objective that the fire extinguishing apparatus should operate so rapidly after the start of a fire that combustion is terminated before the, fire reaches damaging proportions. To accomplish this, the system must perform two functions: firstly it must deliver a fire controlling and extinguishing agent directly to the fire with sufficient force to overcome the pressure of rapidly expanding gases inherent in any explosive combustion. Secondly, the apparatus must deliver the extinguishing agent in large 3,135,330 Patented June 2, 1964 "ice vided a control valve having a. closure member released for movement by a small explosive cartridge which is detonated by electrical detection apparatus suitable for almost instantaneously detecting very small fires. The

control valve closure member is of the type responsive to line pressure of the extinguishing agent. The portion of 'the conduit downstream of the control valve to the blowoff cap is maintained filled or primed with the extinguishing agent at a pressure substantially less than that of the extinguishing agent at its source.

By this arrangement maximum speed is achieved'in getting the fire extinguishing agent to the fire. The flow of electricity in the detection apparatus circuit to the exenough quantity to deluge the burning material so.

thoroughly that combustion is instantly terminated, and thereafter cool the combustible material to a point below its ignition temperature in order to prevent re-ignition.

tected equipment.-

These objectives were successfully attained in our prior system by providing apparatus which comprises generally a conduit leading a fire controlling and extinguishing agentfrom a source under pressure to the equipment where the explosive material is located, a discharge nozzle on the end of the conduit, and a blow-oii cap on the nozzle. Upstream of the. discharge nozzle there is proplosivecartridge of the control valve is almost instantaneous following detectionof a fire. The valve cartridge fires immediately thereafter. The valve closure member is released in an extremely short time. because the force produced by the explosive cartridge is created immediately and is substantial; The blow-off cap begins ,to move olf the discharge end of the conduit immediately after the valve closure member is released, because the very first movement of this closure member in turn moves the priming fluid in the conduit downstream of the control principally toward reducing the time interval between the detonation of the explosive cartridge andthedischarge of water from the nozzle. This time interval is referred to. as the water delivery time. Since the detection apparatus operates with the speed of light, and since the mechanical release of the control valve closure member is substantially instantaneous, the major factor affecting the water delivery time is the static inertia of the standing body of water in the system. conduit between the nozzles and a. point beyond which thisbody of water can no longer be considered isolated from the water supply, for example, the point of connection of the systemconduit to ,the city water main. The more rapidly this static inertia can be overcome and the body of water accelerated from its standing condition to itstterminal velocity, the shorter will be the water delivery time. Since the rate of acceleration of the standing body of water is a function of the pressure at the source, the water delivery time is increased from 50 p.s.i. to psi. the water delivery time is decreased by about 30%.

Unfortunately, the manufacturers of rocket propellant fuels are presently unable to provide exact figures on how fast water must be applied to the fuel mixture in order to have a good chance for fire extinguishment. The reason for this is that the many variables involved, such as the geometry of the propellant, the location and type of ignition initiator, the initial temperature of the grain and the extent of confinement of the propellant and consequent pressure build-up, all serve to make the development of generally applicable values virtually impossible. Hence it is the concern of the fire protection engineer to devise a system which will operate in the fastest possible time, with due regard for reliability of operation and economy of manufacture and installation.

In most installations, the water source is either the city water service or a large capacity fixed water supply maintained at a constant pressure, usually gravity pressure created by an elevated storage tank. In either of these situations it is usually impractical and often impossible to raise the pressure of these water sources to a level which would produce the desired diminution in Water delivery time from that resulting from the normal pressures at which these sources are maintained.

Accordingly, the invention of our present system contemplates the incorporation into ourprior system of an auxiliary source of water of limited quantity which is maintained at a substantially higher pressure than that of the primary water supply. The auxiliary water supply may be held at a pressure many times that of the primary supply, and is stored in a conveniently located pressure tank which is connected by a branch pipe to the main water delivery conduit at a point upstream from the control valve. Means are provided for limiting the discharge of water from the pressure tank to an amount slightly less than the quantity stored therein so that no gas will enter the main delivery conduit and disturb the uniform discharge of water from the nozzles. Still further upstream from the connection of the branch pipe to the delivery conduit, a check valve is inserted in the delivery conduit; this valve is held closed by the substantially higher pressure in the system on the downstream side than the primary water supply pressure on the upstream side of this valve.

When the cartridge fires as the result of a detected fire' in the propellant mixture, the closure member of the valve and the priming liquid downstream therefrom are forced into motion with tremendous speed by the force exerted thereon by the high pressure of the auxiliary water supply, and water is delivered to the fire in an exceedingly short period of time. The water issues from the nozzles with tremendous velocity and pressure to push through the rapidly expanding gases of the burning material to extinguish the fire and cool the propellant mixture and surrounding equipment. When the auxiliary source of high pressure water has been subsentially but not completely expended, and the pressure in the branch line and storage tank drops to, or below, the pressure of the primary source of water, the check valve opens to permit the primary source to continue delivering water to the fire region for as long as is necessary to assure complete extinguishmentof the fire and adequate cooling of the remaining material and surrounding equipment.

Accordingly, it is an object of the present invention to provide a fire protection system capable of delivering an extinguishing agent to a fire within an exceedingly short interval of time after detection of the fire.

It is another object of the present invention to provide a fire protection system capable of delivering an extinguishing agent to a fire at the highest practicable velocity and pressure to neutralize the effects of rapidly expanding gases emanating from an almost explosive combustion.

It is still another object of the present invention to provide a fire protection system having a primary source of water of unlimited quantity which is maintained at a moderate or readily available pressure, and an auxiliary supply of water of limited quantity which is maintained at a pressure considerably higher than that of the primary supply and which will be delivered to the region of the fire immediately upon actuation of the main control valve.

It is yet another object of the present invention to provide a fire protection system having a primary source of water of unlimited quantity which is maintained at a moderate or readily available pressure, and an auxiliary supply of water of limited quantity which is maintained provide a fire protection system having a primary source of water of unlimited quantity which is maintained at a moderate or readily available pressure, and an auxiliary supply of water of limited quantity which is maintained at a pressure considerably higher than that of the primary supply, and means to limit discharge from the latter supply to an amount less than the total quantity available to prevent the introduction of pressure gases into the main delivery conduit of the system.

Other objects and advantages of the present invention will become apparent from the detailed description which follows when considered in conjunction with the accomat a considerably higher pressure than that of the primary panying drawings.

In the drawings, in which the same reference numerals are used throughout the several views to' indicate like parts:

FIG. 1 is a partially cross-sectioned side elevation view of a systemin accordance with the present invention showing the system protecting a mixing device for solid rocket propellant fuel;

FIG. 2 is an enlarged cross-sectioned side elevation view of the control valve of FIG. 1;

FIG. 3 is an enlarged cross-sectioned side elevation view of the blow-off cap and nozzle of FIG. 1 showing the blowofi cap in place on the nozzle.

Referring now to the drawings and particularly to FIG. 1, there is illustrated a preferred embodiment of a fire controlling and extinguishing system installed in association with apparatus 10 for mixing solid rocket fuel during one stage of its manufacture, which apparently illustrates one environment in which there is a hazard of fire in this material. At this particular stage in the manufacture the solid rocket fuel is in the form of a very viscous liquid 12. Later on its hardens and becomes solid.

The actual mixing takes place in a bowl 14 held in a fixed position with respect to the mixing apparatus by structure not shown. The mixing apparatus includes a motor and gear unit 16 driving a pair of mixing paddles '18. These paddles extend down through a protective plate 20, then through a region 22 surrounded by a skirt 24 and into the bowl 14. The bowl can be lowered from the position shown and can be moved away when mixing is completed by mechanism which is not shown.

The danger is that during mixing a fire will start in the material in the bowl, for example by one of the paddles striking a spark from a piece of tramp metal or other foreign substance which accidentally enters the material despite precautions taken to prevent this. Once started, a fire in this material grows with tremendous speed, and if no rapid and effective controlling and extinguishing apparatus is provided, the fire completely ruins the mixing apparatus in a very short time and even the building in which he appatratus is housed.

The fire protection apparatus comprises generally a suitable source of water under pressure, a conduit for leading the water to the fire region, a control valve in the conduit, and fire detection apparatus for actuating the control valve to cause water delivery when a fire is detected. More specifically, the numeral 30 indicates a main water delivery conduit connected at 32 to the city water service or other suitable substanialtly unlimited quantity of water which is maintained under pressure. A control valve 34 is located in conduit 30 to block the passage of water therethrough when the valve is closed. Downstream from the control valve 34, the conduit 30 is divided into a plurality of branches which partially surround the skirt 24 of the mixing apparatus, and these branches in turn have branch pipes 36 which project through the skirt 24 and terminate in a plurality of discharge nozzles 38 situated as close to the combustible material as is practicable. It should be noted that some of these nozzles are directed downwardly toward the fuel mixture, while others are directed. upwardly toward the operating equipment to keep this equipment cool during a fire. 0f course, it is to be understood that the particular number and location of the header 92.

nozzles is determined by the nature of the hazard being I protected, and the arrangement shown is merely illustrative.

Suitable electric eye devices 49 are arranged within the mixing apparatus to detect the minutest fire starting in the material. Suce fire causes the electric eye device 40 to send an electric impulse through the leads 42 to amplification equipment (not shown) which amplifies the impulse and feeds it through leads 44 to the control valve to actuate his valve in a manner here'mafter described thereby permitting water flow through the conduit 30 to the discharge nozzles 38.

In order to reduce to a minimum the water delivery time, the entire piping system downstream from thecontrol valve 34 to the discharge nozzles 38 is filled or primed with water which is maintained at a substantially reduced pressure from that on the upstream side of valve 34. Accidental-discharge of this priming fluid is prevented by blow-off caps 46 (FIG. 3) placed over the ends of the nozzles. The priming is accomplished by means of the by-pass line 48 and by-pass valve 50 so that the control valve 34 need not be opened for priming purposes. The importance of complete priming is better appreciated when it is understood that-an air pocket in the conduit downstream from the control'valve constituting only 5% of this volume will cause approximately a 100% seat portion 52. A body cap 54 is secured to the body 50 by a cap nut 56, the body cap having a central bore to receive the stem 58 of the valve closure member 60 which cooperates with the seat 52 to block the flow passageway.

An O-ring seal 62 seals the closuremember in the seat, and another O-ring seal 64' prevents leakage past. the

stem 58.

The upper end of stem 58 abuts against the lower end of a retaining link 66 which is pivoted at 68 to an upper extension 70 of the body capy 54. Also located in the extension 70 is an explosive cartridge or squib '72 which is received within an opening 74-located adjacent the lower end of line 66. The cartridge 72 is a wellknown device which, when provided with sufficient electric current through the leads 44, explodes to forcibly move the link 66 from its closure member locking position to the position indicated by dotted lines. When the link 66 is thus moved, the valve closure member 60 is free to move up- .wardly under the influence of the upstream line pressure.

'A small switch 76 is conveniently mounted on the extension 70 and has an actuating element 78 adapted to be moved by the link 66 during movement of the latterbetween the positions shown. This switch completes a circuitto an alarm system (not shown) to give an indication that the fire protection system has been, actuated.

Referring again to FIG. 1, the systemin accordance with this invention has an auxiliary water supply generally indicated by the numeral 80. This supply comprises a pressure tank8 2 containing a limited quantity of water which is maintained under pressure supplied by a plurality of cylinders 84 of nitrogen or other suitable gas. The cylinders '84 communicate with the pressure tank 82 through pressure reducers36, header 88, conduit 90 and The pressure tank 82 is connected to the water delivery conduit 34? through a branch conduit 94. A check valve;% is inserted in the water delivery conduit 30 upstream from the intersection of branch conduit 94 with conduit 3!). The check valve 96 has a swing-type closure member 98 therein w hich normally seats against a seating surface formed in the valve body under the influence of a higher pressure on the downstream side than on the up- Stream side.

The operation of the apparatus described is as follows: assuming the primary sourceof water at 32 to have a pressure of 70 p.s.i., the auxiliary supply to be maintained at 250p.s.i.,and the priming liquid downstream of the control valve 34- to be at 5 p.s.i., it is seen that the check valve 96 remains closed due to the pressure differential in the conduit 30 on bothsides of this valve.

When the electric eye device 40 detects a fire, an electric impulse is transmitted to the explosive cartridge 72 through the amplification equipment and leads 42 and 44 to detonate the cartridge, thus releasing the valve closure member 60 for movement. The high pressure from the auxiliary supply 30, acts almost instantly to cause a discharge of water from nozzles 38 with tremendous velocity, pushing off the blow-off caps 46 and entering the region of the fire. The check valve 96 remm'ns closed until substantially all the water in tank82 has been exhausted at which time the pressure in tank 82 and conduit 9 has been reduced to substantially the same pressure as that prevailing at the primary water source 32. At this time, the check valve 96 opens and water continues to fiow through the delivery conduit 30from the'primary water source 32 for as long as is desired.

It-is necessary to assure a reduction of pressure inconduit Maud conduit 30 downstream from check valve 96 to substantially the pressure of the primary water source 32 prior to the complete exhaustion of waterfrom tank 82 and conduit 94. If this is not done, there is risk of the pressure gas from cylinders 84 entering the main delivery conduit 30 with sufficient pressure to keep the check valve 96 closed, thus causing an interruption in the discharge of water at the nozzles. This is accomplished by limiting the supply of pressure gas in cylinders84 in relation to the capacity of tank 82 such that the pressure believed to provide a solution to the problems,'and to fulfill the objectives, hereinbefore set forth. It is to be understood, however, that the above description and accompanying drawings are to be deemed primarily as illustrative of the best mode'presently contemplated of carrying out the principles of. the invention, and that the device described and illustrated may be modified or altered in its form, proportions, detail of construction and arrangement 'of parts without departing fromthe spirit and scope of the'invention as defined in the appended claims.

What we claim and desire to secure by Letters Patent 1s:

1. A fire protection system for highly combustible materials comprising (A) a delivery conduit having (1) one end connected to a primary source of a fire controlling and extinguishing liquid of substantially unlimited quantity under a first pressure and p (2) extending therefrom to adischarge end positioned in a region where said material is located, (B) closure means on said discharge end ofsaid conduit, said closure means being'removable from said discharge end in. response to a predetermined pres: sure in said conduit lower than said first pressure, (C) a normally closed control valve in said conduit, said control valve and said closure means defining a first section of said conduit which is normally filled with said liquid at a second pressure lowerthan said predetermined pressure, (D) fire detecting apparatus in said region and operatively connected to said control valve to actuate said control valve upondetection of a fire in said material,

(B) an auxiliary source of said fire controlling and extinguishing liquid of limited quantity, said auxiliary source of liquid (1) being normally maintained at a third pressure substantially higher than said first pressure and (2) being connected to said conduit upstream from said control valve,

(F) a check valve located in said conduit upstream from said connection of said auxiliary source with said conduit,

(1) said check valve and said control valve defining a second section of said conduit which is normally filled with said liquid at said third pressure,

(2) said check valve being normally held closed by said liquid at said third pressure, and

(G) means for limiting the quantity of discharge of said liquid from said auxiliary source to an amount less than the quantity maintained at said auxiliary source.

2. A fire protection system for highly combustible materials comprising (A) a delivery conduit having (1) one end connected to a primary source of a fire controlling and extinguishing liquid of substantially unlimited quantity under a first pressure and v (2) extending therefrom to a discharge end positioned in a region where said material is located,

(B) closure means on said discharge end of said conduit, said closure means being removable from said discharge end in response to a predetermined pressure in said conduit lower than said first pressure,

(C) a normally closed control valve in said conduit,

said control valve having (1) a closure member mounted therein and being movable in response to liquid pressure thereon, said closure member and said closure means defining a first section of said conduit which is normally filled with said liquid at a second pres sure lower than said predetermined pressure, said control valve further having (2) operating mechanism for normally restraining said closure member against movement and for releasing said closure member for movement,

(D) fire detecting apparatus in said region and operatively connected to said operating mechanism for actuating said operating mechanism upon detection of a fire in said material,

(E) an auxiliary source of said fire controlling and extinguishing liquid of limited quantity, said auxiliary source of liquid (1) being normally maintained at a third pressure which is substantially higher than said first pressure and (2) being connected to said conduit upstream from said control valve closure member,

(F) a check valve located in said conduit upstream from said connection of said auxiliary liquid source with said conduit,

(1) said check valve and said control valve closure member defining a second section of said conduit which is normally filled with said liquid at said third pressure,

(2) said check valve being normally held closed by said liquid at said third pressure, and

(G) means for pressurizing said auxiliary liquid source to said third pressure and for limiting the quantity of discharge of said liquid from said auxiliary source to an amount less than the quantity maintained at said auxiliary source.

3. A fire protection system for highly combustible materials comprising (A) a delivery conduit having (1) one end connected to a primary source of a fire controlling and extinguishing liquid of substantially unlimited quantity under a first pressure and (2) extending therefrom to a discharge end positioned in a region where said material is located,

(B) a blow-01f cap on said discharge end of said delivery conduit, said blow-off cap (1) normally closing said delivery conduit and (2) being removable therefrom in response to a predetermined pressure in said delivery conduit lower than said first pressure,

(C) a normally closed control valve in said delivery conduit, said control valve having (1) a closure member mounted therein and being movable in response to liquid pressure thereon, said closure member and said blow-oi? cap defining a first section of said delivery conduit which is normally filled with said liquid at a second pressure which is lower than said predeterminedlpressure, said control valve further comprising (2) operating mechanism for said closure member, said operating mechanism comprising (a) a locking member normally restraining said closure member against movement and (b) an explosive cartridge operable when detonated to move said locking member to release said closure member for movement,

(D) fire detecting apparatus in said region and operatively connected to said explosive cartridge to detonate said cartridge upon detection of a fire in said material,

(E) an auxiliary source of said fire controlling and extinguishing liquid, said auxiliary source comprising (1) a pressure tank substantially filled with said liquid, said liquid being maintained in said tank under a third pressure which is substantially higher than said first pressure, and

(2) a" branch conduit connecting said pressure tank with said delivery conduit upstream from said control valve closure member,

(F) a check valve located in said delivery conduit upstream, from said connection of said branch conduit with said delivery conduit,

(1) said check valve and said control valve closure member defining a second section of said delivery conduit which, with said branch conduit, is normally filled with said liquid at said third pressure,

(2) said check valve normally being held closed by said liquid at said third pressure,

(G) means for storing a quantity of gas at said third pressure, said quantity being insuflicient to fill said tank when the pressure of said gas therein is reduced to said first pressure as the result of discharge of liquid from said tank, and

(H) means communicating said storing means with said tank.

4. A fire protection system for highly combustible materials comprising (A) a delivery conduit having (1) one end connected to a primary source of a fire controlling and extinguishing liquid of substantially unlimited quantity under a first pressure and (2) extending therefrom to a discharge end positioned in a region where said material is located,

(B) a blow-off cap on said discharge end of said delivery conduit, said blow-oif cap (I) normally closing said delivery conduit and (2) being removable therefrom in response to a predetermined pressure in said delivery conduit lower than said first pressure,

(C) a normally closed control valve in said delivery conduit, said control valve having (1) a closure member mounted therein and being movable in reseponse to liquid pressure thereon, said closure member and said blow-ofl? cap defining a first section of said delivery conduit which is normally filled with said liquid at a second pressure which is lower than said predetermined pressure, said control valve further comprising I (2) operating mechanism for said closure member, said operating mechanism comprising (a) a locking member normally restraining said closure member against movement and (b) an explosive cartridge operable when detonated to move said locking member to release said closure member for movement, (D) fire detecting apparatus in said region and operatively connected to said explosive cartridge to detonate said cartridge upon detection of a fire in said material, (E) an auxiliary source of said fire controlling and extinguishing liquid, said auxiliary source comprising (1) a pressure tank substantially filled with said liquid, said liquid being maintained in said tank at a third pressure which is substantially higher than said first pressure, and (2) a branch conduit connecting said pressure tank with said delivery conduit upstream from said control valve closure member, (F) a check valve located in said delivery conduit upstream from said connection of said branch conduit with said delivery conduit,

(1) said check valve and said control valve closure member defining a second section of said delivery conduit which, with said branch conduit, is normally filled with said liquid at said third pressure,

(2) said check valve normally being held closed by said liquid at said third pressure, and

(G) means for pressurizing said pressure tank to said third pressure to efiect dischargeof said liquid therefrom when said control valve closure member is released for movement and for limiting said eifect to discharge only a substantial portion of said liquid from said tank.

5. A fire protection system as set forth in claim 4 15 wherein said pressurizing and discharge limiting means comprises (A) means for storing a quantity of gas at said third pressure and (B) means communicating said storing means with said pressure tank,

(C) said stored quantity of said gas at said third pressure being insufficient to equal the combined volume of said pressure tank, said communicating means and said storing means when the pressure of said gas is reduced to said first pressure as the result of simultaneous discharge of liquid from said tank and ingres of gas into said tank.

References Cited in the file of this patent UNITED STATES PATENTS Rider July 4, 1944 3,064,739 Hanson et a1 Nov. 20,- 1962 

1. A FIRE PROTECTION SYSTEM FOR HIGHLY COMBUSTIBLE MATERIALS COMPRISING (A) A DELIVERY CONDUIT HAVING (1) ONE END CONNECTED TO A PRIMARY SOURCE OF A FIRE CONTROLLING AND EXTINGUISHING LIQUID OF SUBSTANTIALLY UNLIMITED QUANTITY UNDER A FIRST PRESSURE AND (2) EXTENDING THEREFROM TO A DISCHARGE END POSITIONED IN A REGION WHERE SAID MATERIAL IS LOCATED, (B) CLOSURE MEANS ON SAID DISCHARGE END OF SAID CONDUIT, SAID CLOSURE MEANS BEING REMOVABLE FROM SAID DISCHARGE END IN RESPONSE TO A PREDETERMINED PRESSURE IN SAID CONDUIT LOWER THAN SAID FIRST PRESSURE, (C) A NORMALLY CLOSED CONTROL VALVE IN SAID CONDUIT, SAID CONTROL VALVE AND SAID CLOSURE MEANS DEFINING A FIRST SECTION OF SAID CONDUIT WHICH IS NORMALLY FILLED WITH SAID LIQUID AT A SECOND PRESSURE LOWER THAN SAID PREDETERMINED PRESSURE, (D) FIRE DETECTING APPARATUS IN SAID REGION AND OPERATIVELY CONNECTED TO SAID CONTROL VALVE TO ACTUATE SAID CONTROL VALVE UPON DETECTION OF A FIRE IN SAID MATERIAL, (E) AN AUXILIARY SOURCE OF SAID FIRE CONTROLLING AND EXTINGUISHING LIQUID OF LIMITED QUANTITY, SAID AUXILIARY SOURCE OF LIQUID (1) BEING NORMALLY MAINTAINED AT A THIRD PRESSURE SUBSTANTIALLY HIGHER THAN SAID FIRST PRESSURE AND (2) BEING CONNECTED TO SAID CONDUIT UPSTREAM FROM SAID CONTROL VALVE, (F) A CHECK VALVE LOCATED IN SAID CONDUIT UPSTREAM FROM SAID CONNECTION OF SAID AUXILIARY SOURCE WITH SAID CONDUIT, (1) SAID CHECK VALVE AND SAID CONTROL VALVE DEFINING A SECOND SECTION OF SAID CONDUIT WHICH IS NORMALLY FILLED WITH SAID LIQUID AT SAID THIRD PRESSURE, (2) SAID CHECK VALVE BEING NORMALLY HELD CLOSED BY SAID LIQUID AT SAID THIRD PRESSURE, AND (G) MEANS FOR LIMITING THE QUANTITY OF DISCHARGE OF SAID LIQUID FROM SAID AUXILIARY SOURCE TO AN AMOUNT LESS THAN THE QUANTITY MAINTAINED AT SAID AUXILIARY SOURCE. 